The use of metal microsieves in red blood cell filtration

Purpose of the study was to investigate the sensitivity of metal microsieves (pore diameter 4.3±.2 µm) for detecting changes in red cell deformability through red cell filtration by the hydrostatic pressure of the sample in the MF4 filtrometer. To estimate the effects of pore clogging and of single pore conductance separately in the MF4 filtrometer, a new method of evaluation was introduced and validated using the St. George’s filtrometer. To test the microsieves in the MF4 filtrometer, normal red blood cells (haematocrit 6%) were filtered in parallel with artificially abnormal cells: Internal viscosity and cell volume were altered by changing suspension osmolality, membrane stiffness by heat treatment, and cell shape by incubation with Na-salicylate or chlorpromazine. The induced abnormalities caused a change in single pore conductance or clogging rate and were more easily detected by filtration through metal microsieves than through polycarbonate membranes. Hence, metal microsieves proved a useful tool in red cell filtration.